ES6 : sorting an array based on another array order

Question

sortedArray = [{id: 1}, {id: 2}, {id: 3}, {id: 4}]
unSortedArray = [{id: 8, text : 'abcd'}, {id: 4, text : 'ab'}, {id: 1, text : 'cd'}, {id: 2, text : 'def'}, {id: 3, text : 'abcd'}, {id: 5, text : 'abcd'}]

I want to sort unSortedArray based on items of sortedArray and want only object which has same id as in sortedArray

Result expected

[{id: 1, text : 'cd'}, {id: 2, text : 'def'}, {id: 3, text : 'abcd'}, {id: 4, text : 'abc'}]

I have tried similar suggestions based on similar questions. Adding link of such question here

what did you try so far? – Kristianmitk Mar 23 '20 at 07:44 — Kristianmitk, Mar 23 '20 at 07:44

Jakob E · Answer 1 · 2020-03-23T08:37:50.203

0

Try this

let sortedArray = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }];
let unSortedArray = [
 { id: 8, text: "abcd" },
 { id: 4, text: "ab" },
 { id: 1, text: "cd" },
 { id: 2, text: "def" },
 { id: 3, text: "abcd" },
 { id: 5, text: "abcd" }
];

// Method 1 - Reduce
let sorted = sortedArray
 .map(itm => itm.id)
 .reduce((acc, id) => acc.concat(unSortedArray.filter(itm => itm.id === id)), []);

console.log(sorted);

// Method 2 - Map + flat
sorted = sortedArray
        .map(a => unSortedArray.filter(b => b.id === a.id))
        .flat();
;

console.log(sorted);


// Method 3 - flatMap
sorted = sortedArray
        .flatMap(a => unSortedArray.filter(b => b.id === a.id))
;

console.log(sorted);

edited Mar 23 '20 at 08:37

answered Mar 23 '20 at 07:57

Jakob E

4,476
1
18
21

I'd make it even simpler and use `.map` from `sortedArray` to entries in `unSortedArray`. No real need for `reduce` here. – VLAZ Mar 23 '20 at 08:00
You are right – I've updated the snippet (including flat) – Jakob E Mar 23 '20 at 08:27
If mapping one to many, you can just use `.flatMap`. But if it's just 1:1 mapping them `a.map(x => b.find(y => ))` suffices. – VLAZ Mar 23 '20 at 08:29
It all boils down to browser support :) – Jakob E Mar 23 '20 at 08:31
I don't think a browser that supports `flat` will not support `flatMap` or vice versa. – VLAZ Mar 23 '20 at 08:32
It seems you're right :) – Jakob E Mar 23 '20 at 08:36

score 0 · Answer 2 · answered Mar 23 '20 at 08:13

You could get a hash table first and then map only wanted items.

var sortedArray = [{ id: 1 }, { id: 2 }, { id: 3 }, { id: 4 }],
    unSortedArray = [{ id: 8, text : 'abcd' }, { id: 4, text : 'ab' }, { id: 1, text : 'cd' }, { id: 2, text : 'def' }, { id: 3, text : 'abcd' }, { id: 5, text : 'abcd' }],
    items = unSortedArray.reduce((r, o) => (r[o.id] = o, r), {}),
    result = sortedArray.map(({ id }) => items[id]);

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

ES6 : sorting an array based on another array order

2 Answers2